Servlet学习--练习示例总结

时间：2022-10-16 23:55:53

醉了醉了。。本来想测试下Servlet生命周期的，然后调了好久的错误，还是没成功，不知道为什么不能这样做

贴上代码：

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class LifeServlet extends HttpServlet{

	private static final long serialVersionUID = 1L;

	StringBuffer str;

	@Override

	protected void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		str.append("处理Servlet请求-1");

		doPost(request, response);

	}

	@Override

	protected void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		str.append("处理Servlet请求-2");

		response.setCharacterEncoding("utf-8");

		PrintWriter out;

		out = response.getWriter();

		out.println("<html>");

		out.println("<head><title>fuck you</title></head>");

		out.println(str);

		out.println("</html>");

		out.close();

	}

	@Override

	public void destroy() {

		str.append("销毁Servlet");

	}

	@Override

	public void init() {

		str.append("初始化Servlet");

	}

}

我只是想不在控制台打印出来而已，要不要这样啊

另外测试了下客户端跳转request请求是不行的，服务端跳转都可以

贴上客户端跳转 request，session，application三种请求代码示例

import java.io.IOException;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

public class RedirectServlet extends HttpServlet{

	private static final long serialVersionUID = 1L;

	@Override

	protected void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		this.doPost(request, response);

	}

	@Override

	protected void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		request.setAttribute("requestKey", "requestֵ");

		HttpSession session=request.getSession();

		session.setAttribute("sessionKey", "sessionֵ");

		ServletContext application=this.getServletContext();

		application.setAttribute("applicationKey", "applicationֵ");

		response.sendRedirect("target.jsp");

	}

}

另外目标地址（target.jsp）的文件：

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

<h1>目标地址</h1>

request值：<%=request.getAttribute("requestKey") %><br/>

session值：<%=session.getAttribute("sessionKey") %><br/>

application值：<%=application.getAttribute("applicationKey") %><br/>

</body>

</html>

OK，下面贴上服务器跳转对应三种请求的代码示例：

import java.io.IOException;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

public class ForwardServlet extends HttpServlet{

	private static final long serialVersionUID = 1L;

	@Override

	protected void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		this.doPost(request, response);

	}

	@Override

	protected void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		request.setAttribute("requestKey", "requestֵ");

		HttpSession session=request.getSession();

		session.setAttribute("sessionKey", "sessionֵ");

		ServletContext application=this.getServletContext();

		application.setAttribute("applicationKey", "applicationֵ");

		RequestDispatcher rd=request.getRequestDispatcher("target.jsp");

		rd.forward(request, response);

	}

}

可以看出服务器端跳转只是 

	RequestDispatcher rd=request.getRequestDispatcher("target.jsp");

		rd.forward(request, response);

和客户端的不同，所以个人理解也就是客户端跳转应该是服务器通过response返回给客户端，然后客户端对应跳转url

另外：

贴个比较好的理解

1.forward跳转：

a.服务器端跳转，地址栏不改变；

b.执行到跳转语句后马上无条件跳转，之后的代码不再执行(跳转之前一定要释放全部资源)；

c.request设置的属性在跳转后的页面仍可以使用；

d.使用<jsp:param name="参数名" value="参数值" />传递参数。



2.response跳转：

a.客户端跳转,地址栏改变；

b.所有代码执行完毕后跳转；

c.跳转后的页面不能使用上一个页面的request属性；

d.使用地址重写传递参数（response.sendRedirect("URL?参数名＝参数值")）。

说实话里面的细节我也不懂，知道有这么回事就行了

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